알고리즘 - 문자열 섞기, 문자 리스트를 문자열로 변환하기, 문자열 곱하기

def solution(str1, str2):
    str3 = ""
    for i in range(len(str1)) :
        str3+=str1[i]+str2[i];
    return str3

def solution(str1, str2):
    answer = ""
    
    for a,b in zip(str1,str2) :
        answer += a+b
    
    return answer

def solution(str1, str2):
    return "".join( a+b for a,b in zip(str1,str2))

def solution(arr):
    answer = ''
    return ''.join(arr)

def solution(my_string, k):
    answer = ''
    return "".join( my_string for x in range(k))